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Thread: Trying to get a handle on Lowrey's AOC from the early 1980s

  1. #1
    p Piano stefanv's Avatar
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    Trying to get a handle on Lowrey's AOC from the early 1980s

    I recently came across a few threads on the forum about Lowrey's AOC (Automatic Orchestra Control/Automatic Chord Computer), including Andrew Gilbert's brief explanation of what it does. I wanted to understand it further, and looked up one of the patents:

    http://pdfpiw.uspto.gov/.piw?PageNum=0&docid=04508002

    The idea seems pretty straightforward, but what I can't figure out (because my music-theory-fu is weak, no doubt due to a lack of musichlorians) is how some of the harmony notes in Table 1 of the patent (for melody notes played against a C Major chord) were arrived at. Here's the table in question:

    Code:
    Mel C  C# D  D# E  F  F# G  G# A  A# B
    
    (1) A  A# B  C  C  D  D# E  E# G  G  G
    (2) G  G  G  A  A  C  C  C  C  E  E  E
    (3) E  E  E  F# G  A  A  A  A# C  D  C
    (4) C  C# D  D# E  F  F# G  G# A  A# B
    Most of them are obvious, simply being notes taken from the chord itself, but for instance, where did the A accompanying C come from, or the A# accompanying C#, etc. There is some discussion about "passing notes", which I assume these are, but not how they are arrived at.

    The patent also goes on to state that there are additional tables like this for minor, seventh, augmented, and diminished chords.

    Interesting aside: I found it amusing how they worked so hard to get the storage for these tables down, since 720 bytes would simply be way too big.

    PS. I'm currently working on a new organ-top synthesizer based on a Raspberry Pi, and was considering adding some of this functionality to it. I'm quite impressed with the Pi, having found that with carefully written software, it can easily handle 128 note polyphony while doing synthesis (not playing back samples) in real time. I'll be sure to share my project here when it's completed.

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    Moderator andyg's Avatar
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    The notes in that table look really odd. But that's because we appear to be looking at something that's not really AOC. The patent date is 1985, which means that it's for an 'advanced' Harmony system that's intended to replace the original AOC patents. As Yamaha, Technics et al had similar harmony systems by then, I'm not sure how useful or valuable the patent was! The table appears to be for a system that produces a C6th chord from a simple C chord played, but some of the notes added produce diminished 7th chords!
    It's not what you play. It's not how you play. It's the fact that you're playing that counts.

    New website now live - www.andrew-gilbert.com



    Current organ: Roland Atelier AT900 Platinum Edition
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    p Piano stefanv's Avatar
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    Thanks Andrew.

    Do you have any suggestions as to where I might look to get a better idea of how to generate fairly good accompaniment?

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    Moderator andyg's Avatar
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    Nothing in particular comes to mind. What you ideally want is someone with a Lowrey that has the original AOC and who is prepared to hold down some chords and report accurately on what the organ produces via the AOC.
    It's not what you play. It's not how you play. It's the fact that you're playing that counts.

    New website now live - www.andrew-gilbert.com



    Current organ: Roland Atelier AT900 Platinum Edition
    Retired Organs: Lots! Kawai SR6 x 2, Hammond T402, T500 x 2, X5. Conn Martinique and 652. Gulbransen 2102 Pacemaker. Kimball something-or-other.
    Retired Leslies, 147, 145, 760 x 2, 710, 415 x 2.

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    Moderator myorgan's Avatar
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    Quote Originally Posted by andyg View Post
    What you ideally want is someone with a Lowrey that has the original AOC and who is prepared to hold down some chords and report accurately on what the organ produces via the AOC.
    Did someone summon me?

    Michael
    Way too many organs to list, but I do have 4 Allens:
    • MOS-2 Model 505-B / ADC-4300-DK / ADC-5400 / ADC-6000 (Symphony)
    • Lowrey Heritage (DSO-1)
    • 9 Pump Organs, 1 Pipe Organ & 4 Pianos

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    Moderator andyg's Avatar
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    I knew you'd be here somewhere!
    It's not what you play. It's not how you play. It's the fact that you're playing that counts.

    New website now live - www.andrew-gilbert.com



    Current organ: Roland Atelier AT900 Platinum Edition
    Retired Organs: Lots! Kawai SR6 x 2, Hammond T402, T500 x 2, X5. Conn Martinique and 652. Gulbransen 2102 Pacemaker. Kimball something-or-other.
    Retired Leslies, 147, 145, 760 x 2, 710, 415 x 2.

  7. #7
    p Piano stefanv's Avatar
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    If flute tones were used, careful reporting of what is produced wouldn't even be necessary. A simple recording of each type of C chord (major, minor, 7th, augmented, and I forget the 5th one that Lowrey supported), played against each note in one octave (C to B, maybe two octaves higher than the chord) for a few seconds, would suffice, since I could use spectrum analysis to decode what is being played (since my ear isn't good enough).

  8. #8
    p Piano bnelson218's Avatar
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    The original AOC, or automatic orchestra control, simply looked at the chord being played on the lower manual and then added those notes to the note being played on the upper. This is difficult to achieve on vintage Hammond's that switch the raw audio at the key contacts rather than using keyer circuits. I really wanted this effect for my X77-B rebuild, so I designed my own, called Chord Comp. I use a 4066 chip for each key on the UM starting at C2 (any lower than that would be too muddy.) The chip's four switches pass the 8', 4', 2', and 1' frequencies and the chip's trigger pins are then sent B+ by notes played on the LM. It works pretty sell.
    Over the years: Hammond M3, BC, M102, B3, four X77s and three PR-40s, a Thomas Electra and a Celebrity, three Fender Rhodes, Roland HS-10, HP-2000, HP-600, RD-600, JV-880, a thing made by Korg (?), two Leslie 910s, 122, 257, 258, 247, two 142s, and three custom-built Leslies. Wow, way too much money spent!

  9. #9
    p Piano stefanv's Avatar
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    Thanks bnelson. I want to do something a little more sophisticated, taking into account the note being played on the upper manual as well.

  10. #10
    p Piano bnelson218's Avatar
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    Stephan, I've seen your work on your T and realize I'm nowhere near your league in both theory and design. I'm sure you'll come up with something that'll blow us all away.
    Over the years: Hammond M3, BC, M102, B3, four X77s and three PR-40s, a Thomas Electra and a Celebrity, three Fender Rhodes, Roland HS-10, HP-2000, HP-600, RD-600, JV-880, a thing made by Korg (?), two Leslie 910s, 122, 257, 258, 247, two 142s, and three custom-built Leslies. Wow, way too much money spent!

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